This invention relates to reinforcement dowel pins, and, in particular, to reinforcement dowel pins used in concrete surface construction, and methods of making the same.
Concrete highways and other concrete surfaces are often built in sections. Such sections are useful in controlling and addressing thermal expansion of the concrete surface and avoidance of the problems, such as cracking, that can occur when thermal expansion is not controlled. To accommodate for thermal expansion, joints are usually placed between adjacent panels to allow movement in the direction of the roadway between panels while maintaining the correct lateral and vertical locations of each panel to keep the road surface level and in place.
Various types of construction have been used for “joining” these adjacent panels. These methods include the use of:
1. Solid or tubular steel dowel pins;
2. Epoxy coated solid or tubular steel dowel pins;
3. Glass fiber reinforced composite dowel pins; or
4. Stainless steel solid or tubular steel dowel pins.
Solid steel or tubular steel dowel pins, the most commonly used types of dowel pins, corrode rapidly, particularly in an environment were de-icing salts are used to treat the highway. Epoxy coated dowel pins are initially better than uncoated dowel pins in protecting against corrosion; however, the welding of these dowel pins into support structures during road construction and the abrasion resulting from slab (adjacent panel) movement after construction ultimately wear away the epoxy coating and exposes the steel surface. Once the steel surface of the dowel pin is exposed, corrosion becomes an issue, just as with uncoated dowel pins. Glass fiber reinforced composite pins are weaker and more expensive than steel dowel pins, and stainless steel dowel pins are effective, but very expensive.
Some prior art systems have been developed that are directed toward reduction of the corrosion of steel dowel pins. These systems include that of U.S. Pat. No. 2,093,697. The invention of U.S. Pat. No. 2,093,697 provides a joint form for placement between the slabs. The joint form forms a trough pocket for holding a sealing material. The system of U.S. Pat. No. 2,093,697 requires that additional materials, other than the dowel pins, must be installed between the adjacent sections, and is therefore expensive to implement and to install. U.S. Pat. No. 5,183,694 discloses a system that uses electrodes electrically connected to the reinforcement rods. Again, additional materials must be procured, brought to the installation site, and installed, and additional steps are required for installation of this system. Thus, like the system of U.S. Pat. No. 2,093,697, the system of U.S. Pat. No. 5,183,694 is expensive to implement and install.
Thus, it is desired to provide reinforcing dowel pins, such as those used in highway construction or in other concrete surfaces comprising at least two sections, that resist corrosion, without being detrimental to the strength of the dowel pins when compared to the strength of steel dowel pins, and without significantly increasing the cost of the dowel pins. It is also desired to provide a system for joining adjacent sections of concrete that does not require that materials other than the dowel pins be procured, and does not require additional installation steps, to thereby minimize the costs of such a system.